Field of the Invention
Exemplary embodiments of the present invention relate to a pressure sensor, and more particularly, to a pressure sensor with improved assembling performance.
Description of the Related Art
A pressure sensor is a part which is widely used in automobile, environmental equipment, medical instrument, etc. The pressure sensor has been used under conditions such as generation of vibrations, a sudden change in pressure, measurement of a wide range of use temperature, and high-pressure atmosphere.
A specific use example of the pressure sensor will be described below.
Generally, a brake system for deceleration or braking is provided in a vehicle. The brake system may include a pedal for delivering an operating force of a user, a booster and a master cylinder connected to the pedal to form a braking hydraulic pressure, and a wheel brake braking wheels of the vehicle depending on the braking hydraulic pressure input from the booster and the master cylinder.
When a driver steps on a brake pedal to generate a braking force, if a braking pressure is larger than road conditions or a friction force at the wheel brake generated by the braking pressure is larger than the braking force generated from tires or a road surface, a slip phenomenon that the tires slide on the road surface may occur in the brake system.
A steering apparatus is locked in the state in which the brake is operated, such that the driver may not perform the steering in his/her desired direction. Traditionally, to perform the steering upon the occurrence of the slip phenomenon, an anti-lock brake system (ABS) for electronically controlling a brake pedal effort has bee developed.
The anti-lock brake system includes a hydraulic unit equipped with a plurality of solenoid valves, a low-pressure accumulator and a high-pressure accumulator, etc., for controlling a braking hydraulic pressure delivered to a wheel brake and an electronic control unit (ECU) for controlling electrically operated components.
Further, the hydraulic unit is provided with a pressure sensor which senses a brake operating pressure generated from a master cylinder in proportion to the brake pedal effort of the driver and transfers the sensed brake operating pressure to an electronic control apparatus as an electrical signal. The electronic control apparatus controls the brake operation depending on the electrical signal transferred from the pressure sensor.
A detailed structure of the existing pressure sensor performing functions of the above-mentioned example will be described with reference to FIG. 1.
As illustrated, in the existing pressure sensor, a first printed circuit board 20 is disposed over a pressure sensing membrane 11 over a metal diaphragm 10.
Then, ultra bonding and soldering processes are performed, such that the first printed circuit board 20 and the pressure sensing membrane 11 are connected to each other through a lead wire 12. A resistance of the pressure sensing membrane 11 is delivered to the first printed circuit board 20.
A lower portion of the first printed circuit board 20 is bonded to one end of a copper stand 21 by soldering. Further, the other end of the copper stand 21 is welded to the metal diaphragm 10.
A second printed circuit board 40 is disposed over the first printed circuit board 20. A supporter 30 manufactured by plastic injection is provided between the first printed circuit board 20 and the second printed circuit board 40 to maintain an interval between the first printed circuit board 20 and the second printed circuit board 40.
A conductive pin 31 is fixed by penetrating through the supporter 30 to electrically connect between the first and second printed circuit boards 20 and 40 and both ends of the pin 31 form contacts on the first and second printed circuit boards 20 and 40 by a soldering process to electrically connect between the first and second printed circuit boards 20 and 40.
A lower end of the supporter 30 is provided with a bent protruding part 32 and thus the supporter 30 is fixedly assembled in a fixed concave groove 22 formed at a side surface portion of the copper stand 21. An upper end of the supporter 30 is assembled in a spring electrode fixing holder 50 formed at an upper portion of the second printed circuit board 40 and thus the supporter 30 is configured to be disposed in a middle portion between the first and second printed circuit boards 20 and 40.
The second printed circuit board 40 is a final board for providing an output to the outside and an upper portion thereof is connected to a spring electrode 60 for applying an external output and an input voltage. The upper portion of the second printed circuit board 40 is provided with a spring electrode fixing holder 50 for fixing the spring electrode 60 to be fixedly connected to the supporter 30.
To protect an internal structure in which the first and second printed circuit boards 20 and 40, the supporter 30, the spring electrode 60, and the spring electrode fixing holder 50 are assembled, an outer case 70 formed of metal is assembled. The outer case 70 is fixed to the metal diaphragm 10 by welding.
As described above, the existing pressure sensor suffers from the soldering process to electrically connect between the first printed circuit board and the second printed circuit board. To properly perform the soldering process, the second printed circuit board may be maintained in a horizontal state and a state in which it does not rotate.
Therefore, the pressure sensor needs the supporter supporting the second printed circuit board in a horizontal state as described above, and therefore the number of parts is increased, thereby making the assembling process complicated.
In addition, the supporter is necessarily provided with a structure in which the second printed circuit board does not rotate while being supported horizontally, for example, a structure in which a protrusion is formed on an inner circumferential surface of the supporter, a structure in which a groove through which the protrusion is inserted into an outer circumferential surface of the second printed circuit board is provided, etc. For this reason, there is a problem in that a shape of the supporter is complicated.